The present inventive subject matter relates to the controlled electrification of fish barriers in general and the activation and control of barriers when certain objects are present in the water.
The effect of electric currents on fish are well known in the prior art and especially in the creation and implementation of electrified fish barriers. U.S. Pat. No. 5,445,111 (Aug. 29, 1995) to Smith (hereinafter “Smith patent”), which is incorporated herein in its entirety by reference, describes a system where electrodes are configured in a curtain array and/or a picket fence arrangement. As described in the Smith patent, the energized electric field in the water creates a electrical barrier that guides the fish to a desired area (typically a fish ladder) during the period of fish migrations. Electrical barriers are generally more effective at fish entrainment or deterrence, than alternate methods, such as mechanical barriers or by chemical poisoning.
Despite the inherent advantages of electrical fish barriers, there are certain situations in which the electrically generated field needs to be increased, decreased, or eliminated due to the presence of objects proximate to the barrier. For example, in certain situations, a vessel with a conductive hull may be present in the vicinity of the electrical fish barrier. The presence of a vessel will modify the electrical field requiring either an increase or a decrease in the potential difference to maintain the same electrical field. In other situations, there may be swimmers in the vicinity of the electrical field. In this situation the electrical field will also have to be modified to reduce any current effects on the swimmers.
Therefore, what is desired is an apparatus to detect and quantify objects located in the vicinity of an electrical barrier and modify the electrical barrier in response to the measured characteristics of that object.